1. Field of the Invention
The invention relates to a roller assembly intended for agricultural machinery.
2. Description of the Related Art
The rollers of agricultural machinery are conventionally combined with various tools or machines, such as tools for working the soil, seed drills, etc. Most frequently, a machine of this kind comprises a combination of tools carried at the back of a tractor and followed by a roller. The roller serves particularly to press down the soil that has previously been worked by the tools and to regulate the working depth of the tools.
There are numerous types of roller, ranging from the traditional roller consisting of a metal cylinder to more recent rollers which comprise flexible annular elements, such as tyres, treads or the like, threaded on a tube that is rotatably mounted about an axle. They may be, for example, inflated tyres or non-inflated tyres of the semi-hollow type.
The invention relates more particularly to a roller assembly for agricultural machinery, comprising at least one tube around which are threaded pneumatic tyres, as well as two supports adapted to support the tube in rotation about an axle at both ends.
A roller assembly of this type is known particularly from the publication FR-A-2 841 733 in the name of the Applicant. In this known roller assembly the tyres are of the semi-hollow type. They are threaded directly around the tube and are not inflated, thus giving them a certain flexibility. They generally have a dome-shaped profile which enables them to produce furrows in the soil, for example in order to sow seeds using a seed drill arranged at the back of the roller. Moreover, this known assembly is fitted with a braking system for exerting a resistant torque between the tube and the frame of the machine carrying the roller assembly.
Roller assemblies of this kind are complex in design owing to the fact that the rollers have to be capable of advancing on open ground on land that is often irregular, strewn with stones or other debris, and also of travelling on roads, the carriageways of which may have very different profiles, at speeds of possibly up to 40 km/h.
It is common to pair two rollers substantially in axial alignment to enable these two rollers to have different rotational velocities in the event of turning, thus making it easier to turn while reducing friction. In fact it is preferable to have, for example, two rollers 1.5 meters wide rather than one roller 3 meters wide.
Thus, in every case, the roller assembly has to be able to adapt to the irregularity of the ground and the profile of the carriageway of the road on which it is travelling. It is also known for this purpose to provide shock absorbers, as taught by the publication FR-A-2 861 252 in the name of the Applicant. However, these shock absorbers are suitable for narrow rollers and substantially increase the vertical distance and hence the bulk between the roller itself and the frame of the machine.